Fitbit and MFP

I borrowed this from a post "pmowers" made yesterday in response to the same quesiton:

You do not have to enter your calories into both programs. The link between Fitbit and MFP works both ways. If you enter your food into MFP, the summary for your meals will transfer over to Fitbit, just as your steps, activity minutes and exercise minutes from Fitbit will show up in MFP. Both programs will show more detail about their logs, but the important stuff moves back and forth automatically. If you were to put something in both programs, you would be either double-credited (exercise) or penalized (calories).

The Fitbit devices and MFP use different algorithms or calculations to determine the number of calories burnt during the day. MFP has to guess based on how you answered your questions during setup as far as activity levels, exercise frequency, etc. Fitbit on the other hand actually counts the number of steps you take, the activity level, and in some cases, the number of steps climbed as well as your sleep pattern. It keeps a much more accurate running total of what you have burned throughout the day. If you log your lunch before you ate it, you could show that you have eaten more calories than burnt, but later in the day, you may show a deficit as you worked off those future carbs. There is a setting on MFP under devices that will let MFP deduct calories available if you are not moving as much as expected. Otherwise, MFP will "credit" you if you burn more calories according to Fitbit than MFP predicted. This suggests to me that MFP feels that Fitbit provides more accurate calorie burn values than MFP.